US20140316168A1

US20140316168A1 - Process for preparing a mixture of alcohols

Info

Publication number: US20140316168A1
Application number: US14/366,285
Authority: US
Inventors: Didier Morvan; Roland Jacquot; Philippe Marion; Virginie Belliere-Baca
Original assignee: Rhodia Operations SAS
Current assignee: Rhodia Operations SAS
Priority date: 2011-12-20
Filing date: 2012-12-13
Publication date: 2014-10-23
Also published as: WO2013092399A1; AR089345A1; CN104024194A; BR112014015545A8; BR112014015545A2; FR2984312A1; EP2794531A1

Abstract

A process for preparing a mixture (M) comprising at least one alcohol (Aj), wherein said process comprises a reaction for oligomerization in the gas phase of at least one alcohol (Ai), carried out in the presence of a solid catalyst doped with one or more metals, at a temperature greater than or equal to 50° C. and strictly below 200° C. The oligomerization reaction is carried out in the absence of hydrogen.

Description

The present invention relates to a process for preparing a mixture of alcohols.
Industrially, the most important alcohols are ethanol, 1-propanol, n-butanol, alcohols for plasticizers containing a C6-C11 alkyl chain and fatty alcohols containing a C12-C18 alkyl chain, used as detergents. These various alcohols are prepared from fossil resources either via an olefin oxidation route or via the Ziegler process (oxidation of trialkylaluminum) (K. Ziegler et al., Justus Liebigs Ann. Chem. 629 (1960) 1). Alcohols are also used as solvents, diluents for paints (mainly light alcohols bearing a C1-C6 alkyl chain), as intermediates leading to esters, but also as organic compounds, as lubricants or as fuels.
The synthesis of these alcohols often involves several steps and leads to mixtures of alcohols. For example, alcohols bearing a C6 alkyl chain are synthesized by co-dimerization of butene and propene, followed by conversion into a mixture of aldehydes by hydroformylation, before being hydrogenated, finally leading to a mixture of alcohols bearing a C6 alkyl chain. For example, butanol has hitherto predominantly been produced via the process of hydroformylation of propylene, a petroleum derivative (Wilkinson et al., Comprehensive Organometallic Chemistry, The synthesis, Reactions and Structures of Organometallic Compounds, Pergamon Press 1981, 8). Butanol may also be obtained via fermentation processes, which have returned to the forefront as a result of the increase in petroleum raw materials. Acetobutyl fermentation, more commonly known as ABE fermentation, coproduces a mixture of ethanol, acetone and butanol in a weight ratio in the region of 1/3/6. The bacterium that is the source of the fermentation belongs to the family of Clostridium acetobutylicum.
Given the diversity of alcohols required for the chemical industry and the broad range of use, there is therefore a need to develop a simplified process for forming alcohols that leads to good yields and minimizes the mixtures. It is also advantageous to have a flexible process enabling the use of ethanol derived from renewable materials to form heavier biosourced alcohols.
One aim of the present invention is to provide a process for obtaining a mixture of alcohols that is free of aromatic compounds, such as xylene or benzene, and which has a limited number of species chosen from unsaturated alcohols such as crotonyl alcohols (cis and trans), 1-butenol, hexenols and alcohologens such as butanal, hexanal or crotonaldehydes (cis and trans).
An aim of the invention is also to provide a process that allows a substantial economic saving, especially on account of the absence of use of hydrogen for performing the alcohol preparation process according to the invention.
Another aim of the present invention is to provide a process for preparing alcohols, and especially butanol, which is easy to perform.
Furthermore, one of the aims of the invention is to provide a process that affords a saving in space devoted to the equipment, and also a gain in time and facility.
One subject of the present invention is thus a process for preparing a mixture (M) comprising at least one alcohol (Aj), said process comprising a gas-phase oligomerization reaction of at least one alcohol (Ai), performed in the presence of a solid catalyst doped with one or more metals, at a temperature of greater than or equal to 50° C. and strictly less than 200° C., said oligomerization reaction being performed in the absence of hydrogen.
Preferably, the reaction is performed at a temperature from 80° C. to 195° C., in particular from 100° C. to 195° C., preferentially from 150° C. to 195° C., very preferentially from 170° C. to 195° C. and even more preferentially from 170° C. to 190° C.
In the context of the invention, and unless otherwise mentioned, the term “alcohols (Ai)” means alcohols whose linear or branched alkyl chain comprises n carbon atoms, with n representing an integer from 1 to 10. According to the invention, the term “alcohols (Ai)” also encompasses the term “starting alcohols”. The “alcohols (Ai)” according to the invention may be, for example: methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, nonanol or decanol. The alcohols (Ai) denote the starting alcohols before the oligomerization step.
In the context of the invention, and unless otherwise mentioned, the term “alcohols (Aj)” means alcohols whose linear or branched alkyl chain comprises m carbon atoms, with m representing an integer from 2 to 20. According to the invention, the term “alcohols (Aj)” also encompasses the term “formed alcohols” or “upgradable alcohols”. The “alcohols (Aj)” according to the invention may be, for example: ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, decanol, ethyl-2-butanol and ethyl-2-hexanol. According to the invention, the mixture (M) advantageously comprises butanol.
In the context of the invention, the alcohols (Aj) are obtained by oligomerization of one or more alcohols (Ai).
In the context of the invention, and unless otherwise mentioned, the term “oligomerization of an alcohol” means a process for transforming an alcohol monomer into an alcohol oligomer. According to the invention, the oligomerization may be, for example, a dimerization.
In the context of the invention, and unless otherwise mentioned, the term “from x to y” means that the limits x and y are included. For example, “an integer from 2 to 20” means that the integer is greater than or equal to 2 and less than or equal to 20.
Preferentially, the alcohol (Ai) is ethanol.
According to a particular embodiment, the oligomerization is a dimerization, preferentially a dimerization of ethanol. In this embodiment, the mixture (M) obtained comprises butanol.
According to a particular embodiment, the present invention relates to a process for preparing a mixture (M) comprising at least one alcohol (Aj), said process comprising a gas-phase ethanol dimerization reaction, performed in the presence of a solid catalyst doped with one or more metals, at a temperature of greater than or equal to 50° C. and strictly less than 200° C., said dimerization reaction being performed in the absence of hydrogen.
According to the invention, the alcohol(s) (Ai) used may be anhydrous or aqueous. If the alcohol(s) (Ai) used are aqueous, they may comprise from 0.005% to 20% by weight of water relative to the total weight of alcohol(s) (Ai).
In the context of the invention, and unless otherwise mentioned, the term “solid support” means a mineral compound advantageously having acid-base properties.
In the context of the invention, and unless otherwise mentioned, the term “doped solid catalyst” means a solid support that has been modified, and more particularly doped, with a dopant, such as one or more metals. Preferably, said solid support present in the doped solid catalyst lacks, in itself, said dopant.
Thus, a doped solid catalyst corresponds to a solid support as defined above, which has been doped with one or more metals.
According to a particular embodiment, the solid support is an acid-base solid support. In this case, the doped solid catalyst used for performing the process according to the invention is advantageously a doped acid-base solid catalyst.
According to one aspect of the invention, the doped solid catalyst is obtained by doping a solid support with one or more metals, said solid support being chosen from the group consisting of:

- alkaline-earth metal phosphates, especially calcium phosphates such as tricalcium phosphates, hydrogen phosphates or hydroxyapatites;
- hydrotalcites;
- zeolites; and
- mixtures of metal oxides.

Thus, according to the invention, the doped solid catalyst may be chosen from the group consisting of doped alkaline-earth metal phosphates, doped hydrotalcites, doped zeolites and mixtures of doped metal oxides.
According to the invention, the solid support may be chosen from the group consisting of:

- alkaline-earth metal phosphates, especially calcium phosphates such as tricalcium phosphates, hydrogen phosphates or hydroxyapatites;
- hydrotalcites;
- zeolites;
- metal oxides or mixtures of metal oxides.

According to a particular embodiment, the solid support advantageously having acid-base properties is an alkaline-earth metal phosphate, chosen especially from calcium phosphates such as tricalcium phosphates, hydrogen phosphates and hydroxyapatites. Preferably, for these phosphates, it is possible to use these salts with the stoichiometry Ca₃(PO₄)₂, CaHPO₄or Ca₁₀(PO₄)₆(OH)₂or these same non-stoichiometric salts, i.e. with Ca/P molar ratios different from that of their empirical formula, so as to modify the acidity-basicity thereof. In general, these salts may be in crystalline or amorphous form. Some or all of the calcium atoms may be replaced with other alkaline-earth metal atoms without this harming the performance qualities of the final catalyst.
According to another embodiment, the solid support advantageously having acid-base properties is chosen from hydrotalcites. Hydrotalcites or lamellar double hydroxides may have a general formula M²⁺ _1−xM³⁺ _x(OH)₂(Aⁿ⁻ _x/n).yH₂O, with M²⁺being a divalent metal and M³⁺a trivalent metal; A being either CO₃ ²⁻in which n=2, or OH⁻in which n=1; x is from 0.66 to 0.1 and y is from 0 to 4. Preferably, the divalent metal is magnesium and the trivalent metal is aluminum. In the latter case, the empirical formula may be Mg₆Al₂(CO₃)(OH)_16,4H₂O. According to the invention, a modification of the ratio M³⁺/M²⁺may be possible while at the same time maintaining the hydrotalcite structure, which makes it possible to modulate the acidity-basicity of the catalytic support. Another way of modifying the acidity-basicity of this family of supports may be to replace the divalent metal with another metal of identical valency, the same substitution operation being possible with the trivalent metal.
According to another embodiment, the solid support advantageously having acid-base properties is chosen from zeolites. According to the invention, the zeolites are not in their acidic form, but in their sodium form, in which some or all of the sodium ions may be exchanged with other alkali metals or alkaline-earth metals (LiX, LiNaX, KX, X being an anion, for example a halide anion such as chloride). These supports may be prepared by cation exchange using zeolites in sodium form and a solution containing the cations to be introduced in the form of a water-soluble salt, such as chlorides or nitrates.
According to another embodiment, the solid support advantageously having acid-base properties is chosen from metal oxides, especially metal oxides such as Al₂O₃in alpha or gamma form, SiO₂prepared by precipitation or pyrogenation, TiO₂in anatase or rutile form, preferentially anatase form, MgO, BaO or CaO. These oxides may be supplemented with alkali metal elements so as to modulate their acidity-basicity.
According to another embodiment, the solid support advantageously having acid-base properties is chosen from mixtures of metal oxides, especially binary mixtures of metal oxides such as ZnO and Al₂O₃, SnO and Al₂O₃, Ta₂O₃and SiO₂, Sb₂O₃and SiO₂, MgO and SiO₂, or Cs₂O and SiO₂, so as to obtain a support with bifunctional properties. Ternary mixtures of metal oxides may also be used, such as MgO/SiO₂/Al₂O₃. Depending on the reaction conditions, the ratio of the two oxides present in a binary mixture may be modified as a function of the specific surface areas and of the strength of the acidic and basic sites.
According to the invention, all of the solid supports mentioned above are advantageously in the form of beads, extrudates, lozenges or any other form enabling them to be used in a fixed bed. Advantageously, said support present in the doped solid catalyst is put in form, for example in the form of beads, extrudates or lozenges.
According to a particular embodiment, the solid support is of alkaline-earth metal phosphate type, especially calcium phosphate. Preferably, the solid support is chosen from calcium hydroxyapatites. In this case, the doped solid catalyst is chosen from doped calcium hydroxyapatites.
In particular the molar ratio (Ca+M)/P of the calcium hydroxyapatite before doping (with Ca representing calcium, P representing phosphorus and M representing a metal) is from 1.5 to 2, preferably from 1.5 to 1.8, preferentially from 1.6 to 1.8 and even more preferentially from 1.7 to 1.75. According to the invention, M may represent a metal, a metal oxide or a mixture thereof, ranging from 0.1 mol % to 50 mol % of calcium substitution, preferably from 0.2 mol % to 20 mol %, M preferentially being chosen from Li, Na and K.
According to one embodiment, the solid support advantageously having acid-base properties is doped with one or more transition metals, more preferentially with transition metals chosen from the metals Ni, Co, Cu, Pd, Pt, Rh and Ru. According to the invention, the metals may be used alone or as a mixture.
According to the invention, the doping may take place via methods known to those skilled in the art, for instance by coprecipitation during the synthesis of the doped catalyst or by impregnation, on the already-prepared solid support, of at least one precursor of said dopant, preferentially of said transition metal. The content of dopant, preferentially of transition metal, may be adapted by a person skilled in the art, but it is generally from 0.5% to 20% by weight, preferably from 1% to 10% by weight and preferentially from 1% to 5% by weight relative to the weight of the doped solid catalyst.
Preferentially, the solid support is doped with nickel.
According to the invention, the doped solid catalyst may be calcined and at least partially reduced, to obtain, at least partly at the surface of the doped solid catalyst, the transition metal in an oxidation state of zero.
According to a particular embodiment, when the catalyst is doped with nickel, calcined and at least partially reduced, it has at least partly at its surface, nickel in an oxidation state of zero.
According to the invention, the oligomerization and especially the dimerization reaction may be performed at a pressure from 0.1 to 20 bar absolute (1 bar=10⁵Pa), preferably from 0.3 to 15 bar absolute, preferentially from 0.5 to 10 bar absolute and more preferentially from 1 to 5 bar absolute.
In the oligomerization and especially the dimerization reaction of the process of the invention, one or more alcohols (Ai), especially ethanol, may be fed continuously as vapor phase. The flow rate of alcohol(s) (Ai) of said reaction may be from 1 to 8, preferably from 1 to 6 and preferentially from 1 to 5 g of alcohol (Ai) per hour and per g of doped solid catalyst.
According to one embodiment, the oligomerization and especially the dimerization reaction may be performed in the presence of an inert gas, such as nitrogen. In this case, the molar ratio between the inert gas, such as nitrogen, and the alcohol(s) (Ai) may be from 0.5 to 10, preferably from 1 to 8 and preferentially from 2 to 6.
In the context of the invention, and unless otherwise mentioned, the term “production efficiency” means the measurement of the efficacy of the process. The production efficiency according to the invention corresponds to the amount of an alcohol (Aj), especially of butanol, produced per hour, for one gram of catalyst used in the process.
In the context of the invention, and unless otherwise mentioned, the term “yield” means the ratio, expressed as a percentage, between the obtained amount of product and the desired theoretical amount.
In the context of the invention, and unless otherwise mentioned, the term “selectivity” means the number of moles of alcohol (Ai), and especially of ethanol, transformed into desired product relative to the number of moles of alcohol (Ai) transformed.
In accordance with the process according to the invention, the gas-phase oligomerization and especially dimerization reaction may be performed using any reactor generally known to those skilled in the art.
According to one embodiment, the reaction is advantageously performed in a tubular or multitubular fixed bed reactor, functioning in isothermal or adiabatic mode. It may also be performed in a catalyst-coated exchange reactor.
According to the invention, the doped solid catalyst is preferentially immobilized in a reactor in the form of grains or extrudates or supported on a metal foam.
The process according to the invention directly allows the formation of a mixture of alcohols, by performing only one oligomerization and especially dimerization reaction, without a subsequent hydrogenation step. Thus, the process according to the invention advantageously allows the use of only one piece of equipment, namely only one reactor and only one catalyst, to enable the production of a mixture of alcohols in a single step consisting of an oligomerization reaction. The process according to the invention is also characterized by being performed in the absence of hydrogen. As a result of the economy of use of hydrogen, the process according to the invention allows a substantial economic saving with regard to the existing processes.
According to the invention, after the reaction, a mixture (M′) is obtained, comprising at least one alcohol (Aj).
According to a particular embodiment, the process comprises a step of condensing the mixture (M′), after the oligomerization reaction, so as to obtain the mixture (M), said mixture (M) comprising at least one alcohol (Aj).
In the context of the invention, and unless otherwise mentioned, the term “mixture (M′)” means a mixture derived from the gas-phase oligomerization reaction of at least one alcohol (Ai). The mixture (M′) thus represents a mixture that is gaseous at the reaction temperature.
In the context of the invention, and unless otherwise mentioned, the term “mixture (M)” means a mixture (M′) which has undergone a condensation step after the reaction. The mixture (M) thus represents a liquid mixture.
According to a particular embodiment, the mixture (M′) obtained after the gas-phase oligomerization reaction may be cooled to a temperature from 0° C. to 100° C., so as to condense the gaseous mixture (M′) to a liquid mixture (M).
According to the invention, the mixture (M) may comprise the remainder of unconverted alcohol(s) (Ai), and especially of ethanol, and water derived from the reaction and/or originating from new alcohol(s) (Ai), and alcohols (Aj), especially butanol.
According to a particular embodiment, the mixture (M) obtained according to the process may comprise at least 5% (by weight relative to the total weight of the mixture (M)) of butanol, and preferably at least 8% and preferentially at least 10% of butanol.
In the context of the invention, and unless otherwise mentioned, the term “new alcohol (Ai)” means the alcohol (Ai) used as starting reagent in the oligomerization reaction.
According to one embodiment, the remainder of unconverted alcohol(s) (Ai) may be recycled.
In the context of the invention, and unless otherwise mentioned, the term “recycling alcohol (Ai)” means the remainder of alcohol (Ai) not converted in the oligomerization reaction.
According to the invention, the new alcohol (Ai) differs from the recycling alcohol (Ai).
In accordance with the process according to the invention, said mixture (M) preferentially comprises several alcohols (Aj) whose linear or branched alkyl chain comprises m carbon atoms, with m representing an integer from 2 to 20. Preferably, said mixture (M) comprises at least butanol (m=4). According to another aspect of the invention, the mixture (M) comprises, besides butanol, other alcohols (Aj) whose linear or branched alkyl chain comprises m carbon atoms, with m representing an integer from 2 to 20. More particularly, the mixture (M) may comprise, besides butanol, linear alcohols, such as hexanol, pentanol, heptanol, octanol or decanol, or branched alcohols such as ethyl-2-butanol or ethyl-2-hexanol.
According to one aspect of the invention, the process may comprise, after the oligomerization and especially the dimerization reaction, and the condensation step, successive distillation steps to separate the various upgradable alcohols (Aj) from the mixture (M), and also steps for recycling alcohol(s) (Ai), especially ethanol.
More particularly, the mixture (M) containing the remainder of unconverted alcohol(s) (Ai), especially ethanol, the water derived from the reaction and/or originating from new alcohol(s) (Ai), and the upgradable alcohols, may be separated in a set of distillation columns intended for recovering the upgradable alcohols, removing the water derived from the reaction and the water derived from new alcohol(s) (Ai) (in the case where the alcohol(s) (Ai) used for the oligomerization are aqueous) and optionally recycling the unconverted alcohol(s) (Ai) of the reaction, generally in their azeotropic form.
According to the invention, the oligomerization and especially dimerization reaction, in the absence of hydrogen, may be performed at atmospheric pressure or under pressure.
According to one embodiment, in the case where the reaction is performed under pressure, the mixture (M) derived from the reaction may be depressurized to a pressure making it possible to perform the separation of the water/alcohol(s) (Ai) azeotrope and of the upgradable alcohols.
In the context of the invention, and unless otherwise mentioned, the term “depressurized mixture (M)” means a mixture (M) which has been depressurized after the oligomerization reaction, when the reaction is performed under pressure.
According to the invention, the mixture (M), optionally depressurized, derived from the process, may be directed to a set of two distillation columns denoted C1 and C2, fitted together to obtain three streams:

- F1: the water/alcohol(s) (Ai) azeotrope, and especially the water/ethanol azeotrope, which is recycled;
- F2: the water derived from new alcohol(s) (Ai) and also the water derived from the reaction; and
- F3: the alcohols (Aj), especially butanol.

According to one embodiment, the columns C1 and C2 may be columns with plates or columns with packing.
The presence of the water/alcohol(s) (Ai) azeotrope, and especially the water/ethanol azeotrope, makes it difficult to remove the water from the reaction. To facilitate this separation, the phenomenon of demixing of the alcohol(s) (Aj)/water mixtures may be used. During the distillation to obtain the alcohols (Aj) (F3) at the bottom and the water/alcohol(s) (Ai) (F1) azeotrope at the top, demixing may take place to generate two liquid phases in equilibrium, a phase a rich in alcohol(s) (Aj) and a phase rich in water. This phenomenon may be used to facilitate the separation of various constituents.
The feed may be performed in column C1, at the stage allowing the performance qualities of the assembly to be optimized.
According to the invention, a decanter may be installed at the bottom of column C1, below the feed plate which separates these two liquid phases, or the decanter may be installed inside or outside the column C1. The organic phase, rich in alcohol(s) (Aj), may be recycled as an internal reflux of the column C1 and makes it possible to obtain the mixture of alcohols (Aj) at the bottom of this column C1. The aqueous phase may leave the column C1 and be sent to a column C2 which may be a reflux separation column or a simple stripper. This column C2 may be boiled and may make it possible to obtain at the bottom a stream of water free of alcohols (Ai) and (Aj), and especially free of ethanol and butanol.
According to the invention, the distillate from the column C2 may preferentially be in the form of steam, this column functioning at the same pressure as the column C1. The vapor phase of this column C2 may be sent to the column C1, preferentially to the stage above the stage of the liquid/liquid decanter. The top of the column C1 is standard and may comprise a condenser for obtaining the reflux necessary for the separation. The water/alcohol(s) (Ai) (F1) azeotrope, and especially the water/ethanol azeotrope, may then be obtained at the top. It may be obtained as a vapor phase or as a liquid phase. If it is obtained as a vapor phase, this avoids having to vaporize it before feeding the synthesis reaction, which advantageously makes it possible to reduce the necessary energy consumption.
According to the invention, the alcohols (Aj) (F3) are obtained at the bottom of the column C1. They may be separated by simple distillation in an additional column C3 in order to obtain pure butanol at the top and the other alcohols (Aj) other than butanol at the bottom.
The various alcohols (Aj) may then be separated via successive distillations to obtain these various alcohols in the order of their boiling points.
According to one embodiment, the new alcohol (Ai), and especially the new ethanol, which is pure or containing water and also optionally the recycling alcohol (Ai), especially the recycling ethanol, if it is liquid, may be vaporized and then superheated to the reaction temperature before entering a reactor in which the oligomerization takes place (oligomerization reactor). If the recycling alcohol (Ai), especially the recycling ethanol, is in vapor form, the new alcohol (Ai), and especially the new ethanol, may be vaporized and then superheated to the reaction temperature before entering the oligomerization reactor.
The process according to the invention advantageously allows the formation of desired alcohols in a single step, unlike the standard route using undoped hydroxyapatites, and comprising a dimerization reaction followed by a hydrogenation as in patent application EP 2 206 763. The process according to the invention allows the use of a single catalyst and of a single reactor, and makes it possible to not use hydrogen. It results therefrom that the process according to the invention advantageously allows a saving in space devoted to the equipment, and also a saving in time and in consequent facility.
The process according to the invention advantageously allows a substantial economic saving, insofar as it leads to the production of a mixture of alcohols without using hydrogen. Furthermore, the process according to the invention is a safer process than the existing processes, given the reduction of the industrial risk associated with the elimination of hydrogen.
The process according to the invention advantageously makes it possible to work at much lower temperatures than in a standard dimerization performed with undoped hydroxyapatites, i.e. at a temperature that is strictly less than 200° C., for example 180° C. approximately, instead of approximately 400° C. for the implementation of the existing processes. There is a consequent saving in energy for an industrial process. This also makes it possible to limit the side reactions, which reduce the yields, which may take place in the gas phase at 400° C. Thus, the process according to the invention advantageously makes it possible to prevent the formation of aromatic compounds such as xylene or benzene which are formed in the gas phase at temperatures of 400° C. Now, these products are difficult to separate from ethanol and butanol. Avoiding their formation facilitates the post-reaction separations, which is an advantage from an industrial viewpoint.
Furthermore, the process according to the invention advantageously allows better selectivity. Specifically, doping with metals allows a reduction in the number of species present, especially the intermediate species chosen from unsaturated alcohols such as crotonyl alcohols (cis and trans), 1-butenol, hexenols and alcohologens such as butanal, hexanal or crotonaldehydes (cis and trans).
The examples that follow illustrate the invention without, however, limiting it.

EXAMPLES

Example 1

Synthesis of an HAP Catalyst Doped with 7.5% (by Weight) of Nickel

A nickel solution was prepared by adding 44.8 g of Ni(NO₃)₂.6H₂O to a graduated flask and then making up the volume to 50 ml with demineralized water. 9 ml of this solution were then added slowly, using a syringe, to 20 g of commercial hydroxyapatite (HAP) in extruded form (Ca/P ratio=1.71) in a stirred round-bottomed flask. Stirring was maintained for 30 minutes. The solid was then dried in a muffle furnace at 120° C. for 2 hours, and the solid was then calcined at 450° C. for 2 hours in air, and the solid was finally allowed to return to room temperature. The catalyst thus obtained contains 7.5% by weight of nickel.

Example 2

Synthesis of an HAP Catalyst Doped with 1% (by Weight) of Nickel

A nickel solution was prepared by adding 5.55 g of Ni(NO₃)₂.6H₂O to a graduated flask and then making up the volume to 50 ml with demineralized water. 9 ml of this solution were then added slowly, using a syringe, to 20 g of commercial hydroxyapatite (HAP) in extruded form (Ca/P ratio=1.71) in a stirred round-bottomed flask. Stirring was maintained for 30 minutes. The solid was then dried in a muffle furnace at 120° C. for 2 hours, and the solid was then calcined at 450° C. for 2 hours in air, and was finally allowed to return to room temperature. The catalyst thus obtained contains 1% by weight of nickel.

Example 3

Reaction Performed at 180° C. with an HAP Doped with 7.5% by Weight of Nickel

6 g of catalyst derived from Example 1 were placed in a glass reactor (22 mm in diameter and 20 cm tall) between 7.5 ml (below) and 17 ml (above) of glass powder (300-600 μm). A stream of nitrogen and hydrogen to activate the catalyst was circulated in the reactor at room temperature for 30 minutes. The reactor was then heated at 400° C. for 2 hours, and then placed at 180° C. The hydrogen stream and the nitrogen stream were stopped. The reaction was performed at atmospheric pressure (P=1 bar). Anhydrous ethanol (99.8%) was then added, using a syringe plunger, to the reactor at 180° C., at a flow rate of 11.7 ml/hour. A liquid phase was recovered at the reactor outlet by cooling the collecting flask with cardice. The mixture obtained was injected into a gas chromatograph (GC Agilent HP6890N, HP-innowax (PEG) 30 m×0.25 mm×0.25 μm column, FID detector, cyclohexanol internal standard) for analysis.
The conversion into ethanol is equal to 12% and the weight percentages of the various products are as follows:
Butanol: 5% (52% selectivity)

Acetaldehyde: 0.6%

1-Butenol: 0%

Crotonyl alcohol: 0%
Diethyl ether: 0%

Butadiene: 0.03%

Butanal: 0.18%

Ethylbutanol: 0.5%

Hexanol: 1.05%

Hexanal: 0%

Ethylhexanol: 0.32%

Octanol: 0.32%

Xylene: 0%

Benzene: 0%

A butanol yield of 6.3% and a production efficiency of 0.08 g of butanol per hour and per g of catalyst were obtained.

Example 4

Reaction Performed at 180° C. with an HAP Doped with 1% by Weight of Nickel

6 g of catalyst derived from Example 2 were placed in a glass reactor (22 mm in diameter and 20 cm tall) between 7.5 ml (below) and 17 ml (above) of glass powder (300-600 μm). A stream of nitrogen and hydrogen to activate the catalyst was circulated in the reactor at room temperature for 30 minutes. The reactor was then heated at 400° C. for 2 hours, and then placed at 180° C. The hydrogen stream and the nitrogen stream were stopped. The reaction was performed at atmospheric pressure (P=1 bar). Anhydrous ethanol (99.8%) was then added, using a syringe plunger, to the reactor at 180° C., at a flow rate of 11.7 ml/hour. A liquid phase was recovered at the reactor outlet by cooling the collecting flask with cardice. The mixture obtained was injected into a gas chromatograph (GC Agilent HP6890N, HP-innowax (PEG) 30 m×0.25 mm×0.25 μm column, FID detector, cyclohexanol internal standard) for analysis.
The conversion into ethanol is equal to 11.1% and the weight percentages of the various products are as follows:
Butanol: 6% (63% selectivity)

Acetaldehyde: 0.6%

1-Butenol: 0%

Crotonyl alcohol: 0%
Diethyl ether: 0%

Butadiene: 0.13%

Butanal: 0.2%

Ethylbutanol: 0.4%

Hexanol: 1%

Hexanal: 0%

Ethylhexanol: 0.25%

Octanol: 0.26%

Xylene: 0%

Benzene: 0%

A butanol yield of 7% and a production efficiency of 0.09 g of butanol per hour and per g of catalyst were obtained.

Example 5 (Comparative Example)

Reaction Performed at 220° C. with an HAP Doped with 1% by Weight of Nickel

6 g of catalyst derived from Example 2 were placed in a glass reactor (22 mm in diameter and 20 cm tall) between 7.5 ml (below) and 17 ml (above) of glass powder (300-600 μm). A stream of nitrogen and hydrogen was circulated in the reactor at room temperature for 30 minutes. The reactor was then heated at 400° C. for 2 hours, and then placed at 220° C.
The hydrogen stream and the nitrogen stream were stopped. The reaction was performed at atmospheric pressure (P=1 bar). Anhydrous ethanol (99.8%) was then added, using a syringe plunger, to the reactor at 220° C., at a flow rate of 11.7 ml/hour. A liquid phase was recovered at the reactor outlet by cooling the collecting flask with cardice. The mixture obtained was injected into a gas chromatograph (GC Agilent HP6890N, HP-innowax (PEG) 30 m×0.25 mm×0.25 μm column, FID detector, cyclohexanol internal standard) for analysis.
The conversion into ethanol is equal to 22% and the weight percentages of the various products are as follows:
Butanol: 4.1% (22% selectivity)
Crotonyl alcohols: 0.02%

1-Butenol: 0.035%

Acetaldehyde: 2.05%

Acetal: 0.07%

Diethyl ether: 0.68%

Butadiene: 0.1%

Butanal: 0.43%

Hexanol: 0.9%

Ethylbutanol: 0.5%

Hexanal: 0.13%

Ethylhexanol: 0.26%

Octanol: 0.21%

Xylene: 0.04%

Ethylene: 0.36%

Hexadiene: 0.13%

Benzene: 0.03%

A butanol yield of 4.7% and a production efficiency of 0.06 g of butanol per hour and per g of catalyst were obtained. At this temperature, the selectivity toward butanol is reduced and the range of products identified is broader, especially with many more non-upgradable products such as aromatic compounds (benzene, xylene) and light compounds (ethylene, butadiene, diethyl ether, acetaldehyde, acetal).

Example 6 (Comparative)

Reaction Performed at 150° C. with an HAP Doped with 1% by Weight of Nickel, without Circulation of Gases

6 g of catalyst derived from Example 2 were placed in a glass reactor (22 mm in diameter and 20 cm tall) between 7.5 ml (below) and 17 ml (above) of glass powder (300-600 μm). A stream of nitrogen and hydrogen was circulated in the reactor at room temperature for 30 minutes. The reactor was then heated at 400° C. for 2 hours. The circulation of gases was stopped and the reactor was placed at 150° C. The reaction was performed at atmospheric pressure (P=1 bar). Anhydrous ethanol (99.8%) was then added, using a syringe plunger, to the reactor at 150° C., at a flow rate of 11.7 ml/hour. A liquid phase was recovered at the reactor outlet by cooling the collecting flask with cardice. The mixture obtained was injected into a gas chromatograph (GC Agilent HP6890N, HP-innowax (PEG) 30 m×0.25 mm×0.25 μm column, FID detector, cyclohexanol internal standard) for analysis.
The conversion into ethanol is 2.4% and the weight percentages of the various products are as follows:
Butanol: 1.0% (50% selectivity)

Acetaldehyde: 0.6%

1-Butenol: 0%

Crotonyl alcohol: 0%
Diethyl ether: 0%

Butadiene: 0%

Butanal: 0.1%

Ethylbutanol: 0.1%

Hexanol: 0.3%

Hexanal: 0%

Ethylhexanol: 0.1%

Octanol: 0.1%

Xylene: 0%

A butanol yield of 1.2% and a production efficiency of 0.01 g of butanol per hour and per g of catalyst were obtained.

Example 7 (Comparative)

Synthesis of an HAP Catalyst Doped with 0.05% (by Weight) of Nickel

A nickel solution was prepared by adding 0.240 g of Ni(NO₃)2.6H₂O to a graduated flask and then making up the volume to 50 ml with demineralized water. 3.1 ml of this solution were then added slowly, using a syringe, to 6.0 g of commercial hydroxyapatite (HAP) in extruded form (Ca/P ratio=1.71) in a stirred round-bottomed flask. Stirring was maintained for 30 minutes. The solid was then dried in a muffle furnace at 120° C. for 2 hours, and the solid was then calcined at 450° C. for 2 hours in air, and was finally allowed to return to room temperature.
The catalyst thus obtained contains 0.05% by weight of nickel.

Example 8 (Comparative)

Reaction Performed at 180° C. with an HAP Doped with 0.05% by Weight of Nickel, without Circulation of Gases

6 g of catalyst derived from Example 8 were placed in a glass reactor (22 mm in diameter and 20 cm tall) between 7.5 ml (below) and 17 ml (above) of glass powder (300-600 μm). A stream of nitrogen and hydrogen was circulated in the reactor at room temperature for 30 minutes. The reactor was then heated at 400° C. for 2 hours. The circulation of gases was stopped and the reactor was placed at 180° C. The reaction was performed at atmospheric pressure (P=1 bar). Anhydrous ethanol (99.8%) was then added, using a syringe plunger, to the reactor at 180° C., at a flow rate of 11.7 ml/hour. A liquid phase was recovered at the reactor outlet by cooling the collecting flask with cardice. The mixture obtained was injected into a gas chromatograph (GC Agilent HP6890N, HP-innowax (PEG) 30 m×0.25 mm×0.25 μm column, FID detector, cyclohexanol internal standard) for analysis.
The conversion into ethanol is 1.2% and the weight percentages of the various products are as follows:
Butanol: 0.04% (4.2% selectivity)

Acetaldehyde: 0%

1-Butenol: 0%

Crotonyl alcohol: 0%
Diethyl ether: 0%

Butadiene: 0%

Butanal: 0%

Ethylbutanol: 0%

Hexanol: 0%

Hexanal: 0%

Ethylhexanol: 0%

Octanol: 0%

Xylene: 0%

A butanol yield of 0.05% and a production efficiency of 0.001 g of butanol per hour and per g of catalyst were obtained.

Claims

1. A process for preparing a mixture (M) comprising at least one alcohol (Aj), said process comprising a gas-phase oligomerization reaction of at least one alcohol (Ai), performed in the presence of a solid catalyst doped with one or more metals, at a temperature of greater than or equal to 50° C. and strictly less than 200° C., said oligomerization reaction being performed in the absence of hydrogen.

2. The process as claimed in claim 1, wherein said temperature is from 80 to 195° C.

3. The process as claimed in claim 1, wherein said oligomerization reaction is a dimerization of ethanol.

4. The process as claimed in claim 1, wherein said mixture (M) comprises butanol.

5. The process as claimed in claim 1, wherein said mixture (M) comprises several alcohols (Aj) whose linear or branched alkyl chain comprises m carbon atoms, with m representing an integer from 2 to 20.

6. The process as claimed in claim 1, wherein said doped solid catalyst is obtained by doping a solid support with one or more metals, said solid support being selected from the group consisting of:

alkaline-earth metal phosphates;

hydrotalcites;

zeolites; and

mixtures of metal oxides.

7. The process as claimed in claim 6, wherein said solid support is selected from the group consisting of calcium hydroxyapatites.

8. The process as claimed in claim 7, wherein said calcium hydroxyapatites have a (Ca+M)/P molar ratio is from 1.5 to 2, M being a metal, a metal oxide or a mixture thereof.

9. The process as claimed in claim 6, wherein said solid support is doped with one or more transition metals.

10. The process as claimed in claim 9, said one or more transition metals is selected from the group consisting of the metals Ni, Co, Cu, Pd, Pt, Rh and Ru.

11. The process as claimed in claim 1, wherein said doped solid catalyst is immobilized in a reactor in the form of grains or extrudates or supported on a metal foam.

12. The process as claimed in claim 1, wherein said oligomerization reaction is performed in a tubular or multitubular fixed bed reactor, functioning in isothermal or adiabatic mode.

13. The process as claimed in claim 1, wherein said oligomerization reaction is performed at a pressure from 0.1 to 20 bar absolute.

14. The process as claimed in claim 1, wherein said at least one alcohol (Ai) has a flow rate from 1 to 8 g of said at least one alcohol (Ai), per hour and per g of said doped solid catalyst.

15. The process as claimed in claim 1, further comprising a condensation step after said oligomerization reaction, to obtain said mixture (M).

16. The process as claimed in claim 1, wherein said mixture (M) is subjected to successive distillation steps to separate the one or more alcohols (Aj) from said mixture (M), and also steps for recycling said at least one alcohol (Ai).

17. The process as claimed in claim 1, wherein said solid support is selected from the group consisting of tricalcium phosphates, calcium hydrogen phosphates, and calcium hydroxyapatites.